Commands:
Firework Ride: /tp [PlayerName] @e[type=FireworksRocketEntity]
Particle Trail: /execute [PlayerName] ~ ~ ~ /particle [ParticleName] ~ ~ ~ 0.2 0.2 0.2 0.2 20
Mob Morph 1:st Step: /effect [PlayerName] invisibility 1000000 0 true
Mob Morph 2:nd Step: /tp @e[type=MobName] [PlayerName]
Test For A Block: /testforblock X Y Z [BlockName]

READ: Replace [PlayerName] With Your Minecraft Playername,[ParticleName] With The Particle Effects Name,[BlockName] With The Block's Name & X Y Z With The Coordinates.